Telephone-exchange system



A ril 5. 1927.

F. W.'DUNBAR TELEPHONE EXCHANGE SYSTEM Filed Oct. 9, 1905 2 Sheets-Sheet .1

April 5 1927. 1,623,337

F. W. DUNBAR TELEPHONE EXCHANGE SYSTEM Filed Oct. 9, 1905 2 Sheets-Sheet 2 R\ Q V Q N Kg 5 I? m W262 aYwaW W/YMMV4- eace A li.

UNITED STATES rA'T,

rumors w. Donna, on cnrcaeo, Iimm'ois,

no mess swrrcnnoaan a SUPPLY commmr, a qoaroaarron or TELEPHONE-EXCHANGE sirs'rau.

assmnon; mr menu assremmms, rumors.

Application med 0mm 9, 1905. Serial llo. aaaeow. v

My invention relates to telephone exchan e systems, and has for JlZS ob ects the 'mp ification of-the operators duties and the improvement in uniformity, quickness and effectiveness of service.

Features of my invention are of particular service in connection with multiple switch-' board systems, but my invention in all of its embodiments is not to be hmlted to such practice.

Hitherto in multiple sw1tch-boar( practice, it has been customary for the o erator,

before making connection therewith, al-.

on receiving from the calling subscriber the number of the desired subscribers, manually to test a multi lejack associated with the line of the ca ed subscriber to determine whether or not the line is already bus This test is usually made by applylng the tip of the testing-plugrto the ring or projecting contact of the jac the busy indicatron being generally indicated by a click in the operators telephone and the 1dle condition by the absence of such a click. quires that each operator shall test-each line though only a small per cent. of the calledfor lines are found busy. By my inventlon,

it is no longer necessary for the operator to test the line of a called-for subscriber, but she may make connection with the jack of said line without waiting to make the busy test and without knowing whether or not the line be busy. If the line be idle, the calledfor subscriber will preferably beautomatically signaled and the connection automatically established withoutany further attention on the part of the operator. If, however, the line be busy, the calling subscriber will preferably be automatically and immediately connected to'a source of characteristic disturbance instead of to the called busy line, thus preventing interference with the conversation which may be taking place This ref phone upon hook. The operators thus establish all connections in the same manner without first determining thebusy or idle condition of the called-for lines,'and avoid the delay required by the testing of all called-for subscribers lines. Moreover, in the preferred embodiment of my invention, the disconnecting-signal will be automatically given to the operator as soon as 9. lug has been inserted thus permitting such connection to be immediately taken down.

My invention is particularly applicable to multiple switch-boards involving the automatic distribution of the calling-si als.

In the accompanyin drawings have shown the preferred em odiment of m inyent on as applied to an automatic distrlbut- 1n system wherein the answering-ends of lin -circuits are automatically connected with calling lines. Fig. 1 illustrates m referred arrangement and includes as a distinct eatune of my invention, novel means for automatically selectively signaling any one of a limited number of subscribers on a party km, and for automatically completing con-. nection thereto from a calling subscribers line if the line be idle. Should the called line be busy, the calling subscribers line.

will be automatically released and restored to its normal condition, the disconnectingsignal will be automatically and preferably instantly given to the operator, and-the'callmg subscribers line will be'automatically connected to a characteristic busy source of current variation. I

Fig. 2 indicates an intermediate or indicating position of the party line ringingke s illustrated in Fig. 1.

ig. 3 illustrates another embodiment of m invention, as will be fully explained.

ike parts. are indicated by characters in the figures.

As will appear, the preferred system includes apparatus for immediately disconnecting a calling subscribers line from the answering-ends of a link-circuit connected with a busy called line, irrespective of the calling subscribers apparatus, but I do not wish to be limited to this characteristic in all embodiments of my invention.

' Referring particularly to Fig. 1, I have corresponding illustrated two subscribers lines in process into a jack of a busy ine,

right hand subscriber,

been connected'with a springack belongin to'the line of; subscriber. B. Subscriber hasnot as yet removed'hisftelephone from its hook in to his call s1gnal. I

Each 'subscribers' station may be equipped with one of the customa arrangements of telephone instruments an needs no'further description, and to which my invention is not limited. The circles A A and the which is that belonging to the left hand telephone line 7+8, has already-selected, in

circles B, .-B,- B represents other .sub-

cribers stations which may be connected with the same lines as subscribers A and B,

in the 3 well known manner, Each subscribers line is provided with cut-ofl' rela which may be permanently connected wit 1 1 the sleeve-rings ofthe multiple spring-jacks 2--2 of the correspondingsubscribers line.

In the normal de-energized condition of the relay 1,

its armature-switches 3 -4 make contact with their normal-contacts,

5 and common battery C. hem-therefore,

the calling subscriber A removes his teletare-switch 10,1;6

hone from its book, his-line-relay',5 will he 0 rated from grounded-battery C, over con uctor 6, line-relay5, line-limbs 78,

conductor 9 and its normal-contact of armaground. The operation of relay 5 is, therefore, under the'controlofthe subscriber during the normal condition ofrelay 1; Relay 5 verns the, initial operation of relay 1 1 WhlCh controls theoperation of the motor-magnet 12 through-tl-ie contact of grounded armature-switch13. Each line is provided with a motor-magnet 12, .oper- I atedflfrom the common source of vulsating or intermittent current D,' .and. riving, by means of its spring-armature 14, drivingpawl 14* and toothed-wheel 15, a-seri'es of rotating-arms 16, 17 and 18, carried by the "5 shaft of said wheel and arranged to make tons 19, 20 and 2L Each line is provided with .a 'similar series of buttons19,'-20,,21,

contact, respectively, with the series of butand with a similar set'of annsl16, 17, 18, operated by their respectiveline motor-magnets. Each button-19, each button20and each button 21, represents, respeetiyelflua connection or contact point extendingto th I Q local-conductor, the sleeve-strandandthe tip-f strand, respectively, [ofsome {cord-circuit,

buttons of eac of the line-swi connected 7 U of lines in t e exchange, or if theli'n'es==-be divided into two or more groups, 'a'*cor- 7 res nding grouping of the cord-circuits wi be made and the multiple connections of the series of buttons 19,20 and.21 will be similarly grouped. In'other words, a group F of telephone is associated with a group and having thus ineluding, in circuit withthe line, line-relay of cord or 'Iink circuitsi each line being erably adapted for connectionwith any cordf circuit ofts said group."

Y One complete cord-circuit is-represented' r in Fig. 1', and it'will be understood that the conductors associated with the other buttons 19, 20' and 21, are extended to other similarly equipped cord-circuits; In their normal positions, the arms 16,- 17 and 18 contact with'the buttons 19, 20 and 21 respectively, which are disconnected from' all other but-tons. The left hand switch,

response to subscriber A in calling, the first vided with an enlarged contact-wiper capable of making contact'with a button 19]before breaking contact with the immediately pre ceding-button, or nearly so, whereby-the circuit completed thr'oughthe said arm- 16, 5 while the; arm isrotating jduring selection,

will not be opened a sufiicient lengthof time to .allow the de-energi zation of magnet 11," whosecircuit is then completed through the said arm 16 and associated buttons 19, as will be set forth.

vThe magnet 11 by its operation, not only establishes circuit through themotor-magnet '12, by" the closure of its armatureswitch 13 with its contact to cause the'rotation of the switch as previously set forth, but also opens all connection between the line and travel ing-a-rms l7' -andl8, by causing-the arma-- tures,witches 22 and '23 to leave their contacts; In addition, magnet 11 completes a second circuit for itself through its winding,

armature -switch'27 and its normal-contact, ariiature-switch- 24 and its alternate-contact, the contact-arm-16, buttons 19 and the conductors 25, which are associated with busy cordecircuits and are, consequently, pro; vided with ground'connections, as will be explained at length latenon. The magnet 26 is throwninto circuit when magnet 11 hasbeen-released to its normal position and when battery is thrown back over conductor 250i the cord-circuit then engaged by arms 16,117 and 18. Its operationefiects a sec- ,ond operationofrelay ll-through its arma- 1 tureswitch 27 and alternate-contact, the winding' foi 'saidiz magnet" 26, and either the i contact ofs'witch28'to ground,if said switch be not in its i,-.norm al position, or through altemate-contact' fof armature-switch 29,-

swi'tch 30 3 and its contact, armature-switch 3-1- and its co tg if relay 5 'be a i,

then" energized and if said switch-3O be then in it's normal position. The switches 28 and 30 are operated by the projection 32, carried by the wheelv 15 (or. by other convenient mechanism), when the said wheel reaches its normal position. In the normal position,

as shown in the three right hand wheels,"

switch 30 v,is'closed to its contact and switch 28 is opened from its contact; whereas when the wheel'15 is moved from its normal position in selecting an idle link-circuit, switch 30 is opened from its contact and 'SWlbCh 28 closed to its contact, as shown in the left hand line-switch. It thus follows that when the release-magnet 26 has once been operated by current over conductor 25, in a manner which will later on be explained, it will lock the magnet 11 up through its own winding and either the ground on switch 28 present at all times when the switch-wheel is not in its normal position, or the ground of armature switch 31 when the wheel 15 1s in its normal position and when said armaturtrswitch 35 is attracted; The second energization of magnet 11 causes the continuous rotation of the wheel 15 until the normal position is reached, and. if the line-relay 5 be then energized, said wheel 15 and switcharms 16, 17 and- 18 carriedthereby will continue to rotate during such energizatlon; magnet 26 being maintained in its operated condition'in this circuit, will cause its armature-switch 10 to make contact with its alternate-contact, thus closing circuit from the common battery 0, over conductor 6, through line-relay 5,1ine-limbs 7 and 8, alternate contact of armature-switch 10, and through the interrupter E, bridged by the resistance coil E The interrupter E causes a fluctuation of the current flowing through the calling subscribers station apparatus and may be given any desired rate or period so as to be recognized by the subscriber as a busy indication. It is apparent that this busy indication, in the em odiment of the invention shown, will be re ived by the calhng subscriber whenever agnet 26 is energized and as long as his telephone remains off its hook. The resistance E is suitably proportioned to allow the continued energization of magnet 5 during the interruptions caused by the interrupter E and to graduate the strength of the disturbance in the line. When the calling subscribers telephone is; replaced upon its hook, the line-relay 5 W111 be deenergized because of the opening of its cir-' cuit at the substation and. the opening of the circuit of its armature-switch 31 w1ll allow the release of magnets 11 and 26 when the switch-wheel 15 reaches its normal positions and opens the ground contact at switch 2 Lamp 33 and relay 34 are common to a group of cord-circuits and represent the pilot indication of the supervisory-lamp 35, individual to the particular cord or linkciruit shown. Lamp 36 and relay 37 may be common to a group of cord-circuits and represent the pilot indication of the call lamp 38, individual to the cord-circuit. Lamp 39 represents the supervisory-ramp associated with the called-for subscriber.

40 represents the customary opcrators listening-in key, and 41 the operators telephone apparatus. These parts of -lithe circuit are operated his linerelay 5 in the manner already described at length, it will be seen that a circuit will be established through magnet 11 to operate it over the circuittraceable from grounded battery C, conductor 6, magnet 11, normal-contact of armature-switch 29, closed contact of switch 30 and closed contact of armatlu'c-switch 31, to ground. The corresponding motor-magnet 12 is thus caused to operate from the intermittent or pulsating source of current I) and causes the travel of the wheel 15 and the corresponding contact-arms 16, 17 and 18, as already fully described. The first step of the wheel 15 opens the circuit of magnet 11 through the contact of switch '30, but establishes a new path for the flow of current through said magnet 11 by theway of armature-switch 27, its normal-contact, armature-switch 24 and its alternate-contact, arm 16 and the button 19, if its associated conductor 25 be grounded; If said associated conductor 25 be associated with a busy cord or link-circuit, it will be provided with a ground at either one of several contact points in its associated link-circuit, as will be explained at length later on. It has been assumed that the first three buttons 19, over which the switch-arm 16 has rotated, were busy and that the fourth button 19 was found to be free from ground, thus representing an idle link-circuit. In the idle condition of the cord-circuit,conductor 25 is continued through armature switch 42 of the link-circuit, and its normal contact, to condoctor 43, extending to the chief operator or manager or other convenient point in the exchange room, where it remains normally open at key t. Circuit through magnet 11 is therefore interrupted as soon as contactarm 16 reaches button 19 unprovided with a ground connection. Relay 11 will thus permit the release of its armature-switches to their normal positions. thus closing the line-conductors 45-46, through the normal-contacts of armature-switches 22-23, through the switch-arms 1817, to the cordconductors 47-48 and the associated relays 52 and 51. The motor-magnet 12 will have its circuit opened at the armature-switch 13 and switch-arm 16 will be momentarily connected, through armature-switch 24 and its normal-contact 49, with the direct ound carrTed bytthe armature-switch 31, w ich is still attracted to close its contact. All flow of current is therefore momentarily prevented through magnet 26, switch 28 and -'Were the alternate-contact'49 of armatureswitch 24 andconductor extending to the; normally open; contact of armature-switch 'Sup I I its ground 'contactthe former circuit through contact 49 -forming a short-circuit I 'of'the paththrough contact and said re lay'26. j I

pose two" or more subscribers had removed their telephones at exactly the same instantfor the purpose of initiating a call; that is, sothat two or more initiating jsub-g scribers switch-wheels 15 'and associated arms 16,17, 18 are in exact synchronism.

.31'not provided, it will be perceived that the latter unreleased one of two practically simultaneously releasing armature-switches associated with two simultaneously calling subscribers lines whose switches are;

'thuslin'synchronism and which will, consequently, make simultaneous contact with buttons 19vassociated with the first idle cordcircuit, might cause the operation of the release-magnet 26 associated with the re-.

leased armature-switches 24 by current flow-1' ing'over the circuit traceable from the bat.- teryC, conductor 6, magnet 11' associated with the latter'a'rmature-switch 24, armafture-switch- 27 and its. normal-contact, said armature-switch 24 and its alternate-contact, switch-arm 16, buttons-19', its assoclated confductor 25, tothe switch-arm 16 associated "with the released-armature-switch 24, said' armature-switch 24,-and its normal-contact '50, its associated magnet 26,v tofgroun'dthrough switch 28 associated with said refleased armature-switch 24; This might re- 'sult'in the operation of the said releasew-j'magnet 26 and the-consequentrelease of the line associated therewith and with the said released armature-switch 24, but would 1 I in the selection bythe nevertheless line associated with the unreleased armatum-switch 24 of the next idle cord-circult;

whereby'the former line would receive the busy indication and its subscriber. would replace his telephone uponits book to allow-1 his switch ,mechanis'm tojassume its normal initiate. v llatterline would at once connect with an ldle 'ne-circuit'; The presence, however ofthe 'tion before being able to again call, and'whereby the said conductor extending from the ;-normally I of its associated release-magnet and. will cause the retention of the second-armature:

.switch 24 in its attracted position, due to the ground immediately established on con- (im eaof the selected link-circuit the r'elease'fofthe said first armature switch 24 and thus'insure the-selection of the V first idle link-circuit by the line associated withthe first released armature-switch 24 and the passage'of'the switch associated with the said second armature-switch 24 beyond thenow selected and: busy link-circuit to some subsequent idle link-circuit. In short, this feature of my invention resides in means whereby one of two or more calling lines, whose selecting switches may simultaneously make contact with an idle link-circuit, is

vnuzintained' in connection with a selected link-circuit and the other calling line or other calling lines of this number, are caused to continue their seeking of another idle link-circuit or other .ide link-circuits.

Immediately upon the closing of armature switch 23 to its normal-contact, cit

cuit is completed from battery C, conduc-- for V 6, supervisory-relay 51, sleeve-conductor 48, armature-switch .23, conductor 46 and cut-off relay 1, to ground, thus causing the energization of both relays 51 and .1, the "latter to disconnect theVline-relay 5 and ground branch 9 from the subscribers line:

this opens the ground circuit through arma-- any ture-switch'31. and removes the short-circuit about relay 26. The energization of relay 1 also causes its armature-switches to con f tact with their alternate-stops, thuscontinuing the flow 'of-cu'rrent'frombattery C in a circuit dividing at cut-off relay land "flowing over" the alternate-contact of its armature-switch 4, line-limbs I and 8, conductor 45, armatureswitch'22, tip-conductor 47 andsupervisory relay 52, to ground.

.The'operation of relays 51 and 52 .places.

a ground connection on-conductor 25 by the circuit traceable from the ground of armature-switch 53 and its alternate-contact,

through normally closed contact ofarmature-switch 54, normally closedcont'act of armature-switch 55, alternatecontact of armature-switch 42, to conductor 25, which is now extended by way of arm 16, armature-switch 24, normalcontact 50, relay26,

to the ground ofswitch. 28. Magnet 26 thus carries a ground on'either'end of its circuit and can respond only when conductor 25 is connected with battery and freed from a direct ground connection; The

Ioperationv ofrelay 52causes the illumination of the calling-lamp 38'by current-frombattery Cv flowing over conductor 6, through the saidolamp 38, alternatexontact, of arma- 56, and normal-contact of armatare-switch 57, to. 11nd. The illuniina-- tion of the callin amp 38 (as well as its pilot-lam 36) indicates to the operator that" a 'subscri r has selected and made a 'call on the corresponding cord-circuit] After determining. the number of the desiredsubscriberthe. ordinary manner, the operviously completely depressed the Hilfigator insertsplug 58 into a jack 2 of the called-for line, having preferably prekey 60 corresponding to the party B 0 he desired line, assuming that the system includes a party line which is called. Keys. 8 59, 61 and 62 represent three'other similarly arranged party line ringing-keys corres onding to the other subscribers stations ,13 and B of the party line,the number of keys corresponding to the number of selective stations on the line. -59 60 61 and 62 represent the ringing-generators of var ing frequencies, say, 20, 40, 60 and 80 cyc es per second, corresponding to and connected to the contacts of the ringingkeys 59, 60, 61 and 62, respectively. The depression of the ringing-key 60 not only connects the particular ringing-generator 60 through its contact 60 and conductor 63 to the normally open contact of the armature-switch 64, but also closes circuit from the common-interrupter 65, common to the entire set of ringing-keys, through contact 60 conductor 66- and relay 67, to battery C, whereby-the said magnet 67 alternately attracts and releases its armacorresponding to the ture-switch 64 at a speed determined by the interrupter 65, thus alternately engaging conductor 68 with the ringing-generator 60, or with the tip-strand 69 of the cord-circuit.

In order that the operator may 'know which subscriber of a party line she has last signaled, the actuated-key is made to furnish this indication until the connectingplug is. withdrawn from connection with the called subscribe'rs line. To this end, the actuated ke is operated to an extreme position in or er to impress the calling current upon the called line, in which position it is locked until the called subscriber responds, the called subcriber in responding causing a magnet to effect a shifting of the position of this keynot to its normal position, but to a. position that is neither the normal nor the extreme position, that is, to an indicating position which is preferably intermediate between the said normal and extreme positions. The key mechanism that I have preferably provided for this purpose comprises a strip 60 carrying actuating-wedges 60 and normally pressed against enlargements 60 of the rods .60 surrounded by coiled-springs, said rods 60 being mounted upon a strip 60 that is normally maintained in the position shown in Fig.. 1 by the springs .60. When a key enerator and one of the party line subscri ers is depressed, its

lower free end rides over the corresponding wedge 60, which wedge holds this key in the posit-ion to which it has been actuated. Any companion keys that were previously locked by similar wedges 60 are by this operation released, for the plate 60 is in belonging to an actuate this operation depressed so as to permit the wedges 60" to escape an key previously depresse When, as will hereinafter be set forth, the magnet 84 is energized when the called subscriber responds (or when a busy line is plugged lnto), the plate 60 is attracted and carries with-it plate 60: this movement of these plates, however, being limited by stops. osts 60 are moved downwardly b this operation of the magnet to bring the d etents 61 into position to engage any catch 61 ringing-key, so that while an actuated ringing-key s released by the magnet, it is arrested before it is fully restored or otherwise left in an indicating position.

When a plug is removed from a jack after the CODClIlSlOII of conversation or after connection has been made with a busy line, thus causing the de-energization of magnet 84 and the release of its armature-plate 60 the coiled-springs will cause the restoration of plate 60 also, and thus free any catch 61 from engagement with its spring-detent 61, thus allowing the key to resume its normal position. Should a key fail to restore to its normal position, as would occur after connection had been made with anidle line whose subscriber failed to respond to his calling signal, the operator may secure the complete restoration of the key by momentarily inserting the plug into a special jack 96 whose sleeve-conductor is connected with the battery 0 by the conductor 6 and common resistance-coil 96 thus corresponding to a busy line connectionor by awaiting the following call and depressing the .key corresponding to the new called-for subscriber. The depression of any key will cause'the such companion depressed key or keys, due to the movement of plate 60* and its associated wedges 60 carried thereon. As the spring detents 61 are not moved by barv 60, the restored key cannot be retained in itsindicating or intermediate position, but will be completely restored. In the device shown, the elements 6160-60 are fixed with respect to each other, but are movable with respect to the elements 6060 which latter two elements are movable against the force of the springs 60. 1

I have particularly described one diugrammatic representation of several forms of ringing-key outfits for accomplishing the purpose of my invention, but Ido not wish to be limited thereto, nor do I wish to be 1' lited to the intermediate position of an a 'tuated key as its indicating posit-ions.

If the line into which the plug 58 has been inserted be an idle line, it w1ll be found that the conductor 68 will be connected with the link-circuit, and cut-'ofi relay 1 of the called being connected with the common battery at a oint, for example, that impresses onefo'urt of the total ]potential of said battery and being norma y sleeve-strand 71 by way of the normal-contact of the armature-switch 72 and normalcontact of the armature-switch 73, will have its armature-switch 74 deflected to the left upon the insertion of the plug mto the spring-jack of an idle line, due to the flow' of current over said path and to through the cutofi relay 1 of the cal ed-for line. The closure of armature-switch 74 ound against its left hand 'contact'will cause the energization of magnet 76 from the common source of current C, over conductor 6, through magnet 76 and said armature-switch 74,to'the grounded terminal of said source C, thus causin its alternate-contact, thus locking said magnet 76 over a circuit extending from battery C, conductor 6, magnet 7 6, alternate-contact,

of armature-switch .72, normal-contact of armature-switch 73, sleeve-strand 71 of the for line, to ound, The ener 'zation of ma et 76 wi open the circuit 0 the polari -relay 70 at thenormal-contact of its armature-switch 7 2, thus allowing the arms;- ture switch 74 of polarized-relay 70 to resumeits normal neutral position.

Cut-off relay 1 is also energized by the current .flowing through magnet 7 6, thus causing the attraction of its armatureswitches 3 and 4 to disconnect the line-relay 5 and ground branch 9 from the line and to make contact with their alternate-contacts,

thus.- continuing the link-strands 71 and 71 sleeve-relay 76 and limb 7 of the telephone line, but permits the flow of current from the alternating current-generator conductors 63, 68, line-limb'8,.si nal-bell 80, said cone denser 79, limb 7 to the ground through the cut-ofi relay 1, and also to the ground of the common battery C through sleeve-strand 71 and sleeve-relay '76. Both of said relays 1 and 76 being-now operated bfiebattery cur rent from source C, will not effected by said ringing current. The bell 80 at *the called-for subscribers station will therefore 've its selective-signal (the bells at stations B and Bibeing unresponsive to the. parconnected with the said magnet 76 to attractits armature-switch 72 to make contact wlth ticular rate of 60). Upon t e response of the called-for subscriber-that is, upon his removal of the "telephone from its hookcircuit'from the battery 0 will be established over conductor 6, sleeve-relay 76, sleeve-strand 71, line-limb 7, retardation-coil 81, transmitter 82, line-v limb 8, tip-strand 71 conductor 68, tip-. conductor 69 and tip-relay 78, to ground, when the armature-switch 64 of relay 67 ulsations. sent from generator makes contact with its normal-contact dur- I contact and lock the said relay 84 over the.

said contact of armature-switch 85 and the ground carried by armature-switch 57. .Relay 84 is thus locked through the armatureswitch 57 of relay 76, and cannot be again released until the release of relay 76. The

energization of magnet 84 also causes the attractionof its armature-plate 60 to withdraw-the wedges 60 and allow the release of the. ringing-key 60 to its intermediate position, shown in Fig. 2. In this intermediate position, the key contacts are opened, but said 'key is left in an intermediate or indicating position. This indication now serves to notify the'operator what key had been last depressedthat is, what party1 of the party line had been rung. Prior to; t e energization of relay 78, upon the response of the called-forsubscriber, supervisory-lamp 39 was lighted-as shown in F 1by the closing of armature-switch 57 to its alternate-contact, thus indicating to the operator that the called-for party had not as et responded. Upon the response of the cal ed-for party, the circuit for said supervisory-lamp is openedby the opening of relay armature-switch 83 from its normal-contact. The energization of relay 76 has also caused the attraction of its armature-switch 54 to maintain the ground upon conductor 25 of the cord-circuit through the alternatecontact of armature-switch 42, conductor 88 normalcontact of armature-switch 55 an alternate-contact of armature-switch 54. During conversation, this condition of the apparatus is preserved--the sleeve-strand 71 of the cord-circuit being conductively closed to alternatin +currentsthat is, the.

voice-currentsby t e attraction of armature-switch 89 to its contact. Upon the restoration of the telephone to its hook at the called-for subscribers station, the tip-relay 78 will be. released and its armature-switches restored to their normal positions, thus. again causing the illumination of the super- V180 Jam 39 over its circuit previously trace T e-de-energization of magnet 84 is, however, prevented by its locking circuit through its armature-switch 85, already described. The' ringing-current is thus prevented from being again thrown upon the subscribers line, owing to the continued attraction of the armature-bar 60 and continued opening of the circuit through re- '24,;release-magnet 26, to ground at the switch 28. This causes the energization'of the, release-magnet 26-and the release of the calling subscribers line in the" manner already set forth at length.

When the operator withdraws the connecting-plug from the jack of the called line,

magnet 84 has its circuit opened, as said circuit depends upon the ground connection of armature-switch 57 of relay 7 6--now released; said magnet 84 thereupon releasing its armature-plate 60*, thereby permitting the catch 61" to be disengaged from the detent 61 as previously explained, whereby said key is restored to its normal idle position.

If the connecting-plug 58 had been inserted within the line-jack of a busy line, the greater section of the battery C would have beenincluded in a circuit with the relay 70, which may be traced from the ac- '-tive terminal of said source C, over conductor 6, through relay 76 of the link first associated with the busy-line, its armature-switch 72 and alternate-contact, armature-switch 73 t and its normal-contact, link-strand 71, to

sleeve-ring 75 of the busy line, thence to strand 71 of the link-circuit last connected to the busy line, armature-switch 73 and its normal-contact, armature-switch 72 and itsnormal-contact, through said polarized-relay 7 0 to said battery C, whereby'current is di-' rected through said relay 1n such direction as to cause the armature-switch 74 to swing to the right. whereby the relay 90 is included in a circuit that may be traced from the armature-switch 74, through the winding of said relay, the battery C. back tothe arma ture-switch. The relay 90 attracts its armature-switch '91, which is moved against a ing of the relay 90, thereby establishing a second circuit through said relay which ma be traced from the grounded battery through said relay 90, through its armature-switch 91, the'previously attracted armature-switch 92 and its contact, to ground; circuit through relay 90 is therefore maintained closed as long as the armature-switch 92 of relay 51 is attracted and'the relay 51 'is maintained in (1IC1lltto" maintain attracted the armature-switch 92 as long as the plug 58 is within its jack, for, when therelay 90 is energized, a second circuit .for the relay 51 is established, which circuit may be traced from the groundedbattery 0, through the winding of relay contact that is in connection'with the wind- 51, conductor 93, to the alternate-contzu't of armature-switch 73, thenceby way'of the sleeve-strand 7.1, to ground at the. cutoff relay 1 of the called subscriber. The armature-switch 7 3 is thus maintained away from its normal-contact as long as plug'58 is inserted, so that the polarized-relay 70 is now included in open circuit. 'T he relay 70' cannot therefore be re-operated until after the conne ting-plug is withdrawn and again inserted and is independent of the withdrawal of any other plug from a jack of the busy line. The relay. 90, by closing its armature-switch 55 upon its alternate-contact, effects the disconnection of thesanswering-end of the link from the calling "subscribers line (which, in the embodiment'of the invention shown, is accomplished by rotating the traveling line-terminals of the calling line).v This result is acromplished' by the establishment of a circuit that may be traced from the groululed-battery C, couductor 6, to a portion of the relay 84 which includes, say, a fifth of the resistance of this relay (the relay measuring, for exanx plc, five hundred ohnisor there-abouts), the alternate-contact.ofswitch 55, the conductor 88, the alternate-contact of arn'iature-switch 42, the conductor 25, the selector swit: h-arln 16, the arnmture-switch 24 and its normalcontact 50', the releasing or restoring-magnet 26, the switch 28 and its grounded-contact now engaging the same: the operation of the releasing apparatus and the circuits governing the same now occur as has hitherto been explained, and the calling subscriber Will receive the busy indication and i selecting-motor will continue its operation until he replaces his telephone upon its I hook, ashas also been hitherto explained at length. 4

When the calling subscriber restores his telephone, circuit through magnet 5 is open at his telephone switch-hook. whereby the armature-switch 31 is removed from connection with the contact of switch 30, so that when the selecting-switch again reaches-its normal position, it stops. The calling sub-.

la y scriber should inres onse to the busy indication, restore his te ephone, but should he fail to do so,' the continued operation of his selecting-switch will in no way interfere with the correct operation of the other lines, While in the embodiment of the invention shown in Fi 1 the operation of the travel- .ing-switch or connecting the calling subscriber with a link-circuit does not cease until said subscriber restores his telephone, I do not wish to be limited to a system whereinlthis particular'control is secured.

. It wil1 be seen that the circuit throu h the fifth oft-he winding of relay 84 is on y is busy,

. tact. Supervisory-lamp 39 momentarily closed, and, in order'that said rela may be maintained in operation to shift and hold the actuated ringing-key to anindicating position, circuit through the entire winding of the relay is established from the grounded-battery C through said winding, to. grounded armature-switch 94 and its contact, now closed. The armatureswitch 85 is thereupon attracted to close circuit through the called subscribers supen visory-lamp '39, which circuit maybe traced from the ounded-battery C through the lamp 39, t e released armature-switch 83, the attracted armature-switch 85, to the grounded armature-switch 94 and its conwill therefore be lighted v As will be understood from the.- previous descri tion, the armature-switch 74 of polarize -relay 70 moves'only to the left when the called subscribers line is free and only to the right when the called subscribers line and. the armatureswitch 83 therefore remains nnatttacted when the called line is busy, for the energization of the relay 78 carrying the said armature-switch 83 depends upon the connection of conductor 69.

with the tip-strand 71 which can only be secured by the operation of relay 76 and the closing of its armature-switch 77 a ainst its contact, which, in turn, can only V se- "cured by'the movement of armature-switch 74 to the left, which only occurswhen the called line is idle. p Similarly, the establishment of the circuit for extending the ringing current to the subscribers line depends uponthe en agement of the said armature-switch 77 wit 1 its contact; By maintaining the said switch 77 out-of engagement with its contact, excepting during the connection of its associated link-circuit with an idle line, the ringing current cannot find accem to the line of a busy subscriber, nor' can any other interference, as, for instance, conversation, be

had with a busy line; The calling subscriber being immediately disconnected from 'the link-circuit, interference is further pre' vented with a busy line. The. disconnection of the calling subs'cribers line from the answering-end of the link-circuit also causes cuit. Circuit through relay 51 is, however,

maintained, as previously described, from grounded-battery C to the ground terminal of cut-off relay 1 of the busy subscribers I 7 line, via conductor '93, alternate-contact of armature-switch 73 "and sleeve-strand 71.

'7 Both supervisory lamps 35 and 39 are therefore caused to light as soon as a plug has been inserted into a busy line and the o p ug' from the jack, thus restoring all ap arator will immediately disconnect the its circuit opened at ratus to its normal conditionrelay 51' e- I ing released by the opening of its circuit through conductor 93 and t e cut-off relay of the busy line, and'causing, by the release of its armature-switch 92, the opening of the circuit of relay 90, which, in turn, opens the circuit of relay 84 by the release of its armature-switch 94. The release of magnet 84 causes the complete restoration of the ring'ng-key to its normal position, as heretofore pointed out.

A further purpose of the connection from i the magnet .84 to the alternate-contact of switch 55, is to furnish a ground upon the conductor 25 by way of said switch 55, con ductor 88 and the alternate-contact of switch 42, that will cause the link-circuit whose connecting-plug is inserted in a jack of a busy line, to correspond to a busy link-circuit even thoughthe answering-endflthereof is disconnected from the calling suhscribers line,such busy condition of the link-circuit being thus maintained during the time the connecting-plug is in connection with the busy called line.- This ground is traceable from the ground at switch 94 to the contact engaging the same, four-fifths or other fraction of the winding of magnet 84, to the alternate-contact of armature-switch 55, thence to, the alternate-contact of. armatureswitch 42. it will thusappear that conductor 25 ofa busy link-circuit will always be provided'with a round connection at some point, said point eing at one time at armature-switch 53, at another time at armature switch 54, and at anothertime at armatureswitch 94, thereby causing the rotation of the arms 16,17 and-18 past such busy linkcircuits whilecalling lines are selecting dle lmk-c 1rcu 1ts. i a

Switches 44 aref'pi'ovided to enable the.

vided the link-circuit be then idle, so that.

a traveling-terminal of the calling subscribers selecting-motor upon connection with the button 19 in connection with conductor 25, Will pass said button as if said link-circuit'were already in service.

In case a line is crossed by outside trouble, or in case the receiver at the substation thereof isimproperly off its hook, thus in either case causin the line to initiate a call and select an idle link-circuit, I provide means whereby such aline may be disconnected from the selected link-circuit, said means including a special jack 96 into which the operator may momentarily insert the conmeeting-plug 58 of the selected link-circuit,

,to a particular line posted on each of the subscribers instruments of that line, with inafter finding she can get no response from the apparently calling subscriber. This jack 96 (of which a number may be provided) is provided with a battery connection to its I sleeve-contact as previous described, there- 'by causing the release of the improperly calling subscribers line and the continued rotation of its motor-switch. Other line troubles, such as low resistance ground connections to the line-limbs such as would occur were a cable water-soaked by some accident, would cause the continuousrotation of the motor switches associated with the afl'ected lines without the intervention of the operator, due to the-failure of the tip-relay 52 of a selected link-circuit to become energized, owing to the presence of the practical shortcircuit to ground from the line-limbs, whereby the release-magnet 26 would be immediately operated by current over conductor 25 in the manner previously set forth at length, thus causing the continued operation of the motor-switch. Troubles of the above natures, therefore, indicate themselves by the cont'nuous rotation of the motor-switches of the affected lines. The attendant may then remove the fuses 97 of each such affected line; thus causing the. corresponding motor-switch to stop on reaching its normal position, owing to the opening of the circuit of its associated line-relay 5 at fuse 97, whereby armature-switch 31 is released and the circuit of magnets 11 and 26 opened when the switch reaches its normal position. Moreover, the attendant may then insert test-plug 98 so as to contact with spring 99 and thus connect the t p side of the line-circuit to a source of intermittent current such as the battery C via interrupter 100 and suitable resistance 101whereby when connection is made to such line in trouble by the insertion of a plu 58 intoa jack of'said lme, current from said intermittent source 1s sent over the tip-conductor of said jack to and through the relay 78 of the linkcircuit causing it to intermittently respond and wink the supervisory-lamp 39 to indicate to the operator that the line is in trouble. The calling subscriber will likewise hear the characteristic intermittent current thus thrown on his line circuit through condenser H13 and will understand (even ifnot so informed by the operator) line is in trouble".

It is apparent that should subscriber'A have called for either of the subscribers A,

A or A associated with his own line, and neglected to so inform the operator then as the desired subscribers line would be busy,

the operator, 'on makingthe desired connecs tlon, would merely release the calling subscriber and pull down the connection in response to her disconnecting signal. My invention contemplates, therefore, the inclusion of a list of the other subscriberscommon tions, the release of relay 52, by the open-' mg of the line circuit at the substation would cause a flow of current over the release-wire 25 and magnet 26 from battery C and through lamp 38 in the manner already described at length. The operator is advised of the obedience to her instruction by 'the extinction of the call-lamp 38 and immediately inserts a plu 58 associated with one of-her reserve lin -circuits which the manager or chief-operator has made artificially busyby closing the contact of the switch 44, into a jack of the caled line, having first set the proper ringing key to select the desired party-say, A The line being now idle, the desired party, will be called and, upon his response, the operator may manually momentarily depress the key corresponding to the calling subscriber thus giving him a short ring to notify him that his party has responded. It willbe apparent from Figure 2 that the second key thus depressed will not lock itself in the ringing position but-will return to the indicating position as soon as the operator removes that the desired her linger from it, because ma net 84 is now energized and locked over re ay armaturespring 57 as already described. The operator leaves the plug inserted until the conclusionof conversation-the supervisory lamp 39 .then serving as a special disconnecting signal. The presence of the plug in the jack prevents the operation of the calling-relay 5 and motor-switch of the line in the same manner as described in connection with a regular called line. It is also apparent that the presence of the g ound connection of switch 44 prevents the selection of the. said reserve link-circuit by any other subscriber.

102 represents a section of a distributing board by means of which the various cordcircuits may be distributed to the different operators positions.

It will be apparent that by means of the said distributing board and keys 44. the mana er may secure a distribution of the link-circuits so that all calls will be concentrated toward one end of the switch-board, additional operators being placed in service in regular progression from right to left, or

vice versa, as the businessincreases from hour to hour, and so that each operator on duty may receive as many calls as she is capable of etficiently attending to and no more. Thus, each position may be provided with fifteen link-circuits, but one or several ma be normally made impotent to receive cal s by means of their associated keys 44, whereby each operator may be assigned that number which she is capable of efiiciently handling. It will also be apparent that as a large number of lines may be associated with a particular group of cords-say, one thousand lines for a group of eighty cords (thus requiring eighty-one points or buttons 19, 20 and 21 in each rotating switch) and as the several groups of cords may be so distributed as to give each group of lines equal access to each operator, it necessarily follows that the disconnection of any particular link-circuit, save-one of those at the extreme end of the then busy operators positions, will be immediately followed by its selection by another line for a new call. The operator need not restore the plug to its seat after withdrawing it from a jack, but may throw over her listening-in key to inquire the new number wanted. knowing a succeeding call will imi'nediately occur on the disconnected link. Not having to test the called-for lines, the operators duties are limited to the withdrawal of a plug upon receiving the disconnecting signal, and reinserting it into the jack of the next desired line, setting her selective ringing-key either previous to or subsequent to the insertion of the plug. It will be obvious that although I have described the preferable practice of setting the ringing-key prior to the key subsequent to this operation as an alternative. The operation of the apparatus is the same in either case, save where the plug is inserted into the jack of a busy line. In this case, as the magnet 84 is immediately operated, the ringing-key (should the operator attempt to depress it after inserting the plug instead of withdrawing the plug in response to her disconnecting signal) would not remain in its completely depressed position. but would assume the position shown in Figure 2, and would be restored as usual upon the withdrawal of the pin"; In cithermethod of operation. the released a rmature-switch 7 7 prevents any interference with the busy line, as already described at length. It will be apparent that where party lines are not employed, certain simplifications will result as the selective ringing-keys are not then required. My.invention contemplates such simplifications and other modifications which will be apparent to those skilled in the art.

Figure 3 illustrates a system having many features in common with the system illustrated in Figure 1; and the parts of the system shown in Fig. 3 possessing functions similar to functions possessed by parts in the system of Figure l, are given similar charaeters of reference. Certain characteristics of the system shown in Figure 3 are not disclosed in the system of Figure l and will nowbe set forth.

Fig. 1 illustrates the adaptation of my invention to the so-called two-wire system in which the spring-jacks have but two contact pieces and in which the link-circuit plugs have also but two contact pieces adapted to engage with the corresponding contact pieces of the jacks. In the system of Figure 3, however, the spring-jacks are provided with three cont-act pieces, although the plugs of the link-circuits are provided with but two contact pieces, one of them, the contact piece associated with the sleeve-Ltrand 71, being adapted to cross two of the contact pieces of the jack into which it may be inserted The cut-off relay 1 of each subscribers line, instead of'being connected directly to conductor 46 and to the sleeveconductor 75 of each of the jacks, is normally disconnected therefrom but connected to a third contact piece 75 of each of the spring-jacks. and to a conductor '15 extending to a normally open contact switch 30 associated with the subscribens motor-switch. During the use of the line, however, the said cut-off relay 1 is connected with one side of the talking circuit in either one'of two ways. lVhenever a plug is inserted into a jack, the sleeve-contact of said plug crosses contact pieces 75 and 7 5 of the jack, thus connecting cut-off relay 1 with the sleeve-conductor of the line. Similarly, whenever a 'sub scriber removes his telephone from its hook for the urpose of initiating a call and thus causest e operation of his motor-switch, its first ste will cause its associated switch 30 to close its contact, thereby connecting cut-otf relay 1 with the sleeve-side 46 of the subscribers circuit and maintaining such connection until the motor-switch again resumes its normal position. The-operation of the apparatus directly associated with each subscribers line is the same in other particulars as that indicated in Figure 1, with the exception of a re-arrangen'ient of the contacts associated with the switch 28 controlled by the subscribers motor-switch; the modification merely consisting in transferring the ground connection of armature-switch 31 of Figure 1 to the switch lever 28 of Figure 2, This change in circuit arrangement involves no difference in the method of operation over that explained with reference to Figure 1, and requires no further explanation.

The arrangement of the link-circuits differs, however, from that shown in Fig. 1 in certain respects, which will now be described. In Figure 1, it was assumed that party line subscribers circuits were employed; whereas in Figure 3 it is assumed that individual subscribers lines only are employed, or that all subscribers associated with any particular line will be signaled when any subscribers bell is rung. In the system of Figure 3, it therefore becomes unnecessary to employ selective party line ringing-keys, or, in fayt, any ringing-key manually opera t-ed by ,the operator; the insertion of a plug into a jack of an idle line in itself automatically connecting the ringing-gem erator with the subscribers line. To this end, an additional armature-spring 60" is provided for relay 76 (corresponding to re lay 76 of Figure 1) which will be closed to its contact when relay 76 is energized by the insertion of the plug 58 into an idle line, thus closing the circuit of interrupter I 65 through the said contact of armaturearmature-switch 64 whenever a plug is inserted into an idle line, just as the corresponding relay 67 of Figure 1 was caused to alternately attract and release its armatureswitch 64 as soon as a ringing-key was depressed either before or after the insertion of a plug into its jack. In Figure 3, the ringing-generator 60 is directly connected to conductor 63; whereas, in Figure 1, on

account of a plurality of ringing-genera-- termediate point of its winding whereb tors, said enerator-circuit is closed to conductor 63 y a selecting-key. In other respects, the automatic ringing features of Figure 3 are similar to those already ex plained at length with respect to Figure 1, 1t being apparent that the energization of relay 84 of Figure 3, which is efi'ected at the same time and by the same means as the energization .of relay 84 of Figure 1, will cause the opening of the circuit through relay 67 at armature-switch 60 in Figure 3; just as in Figure 1, the circuit of the said magnet 67 will be correspondingly opened it the contact 60 in the selective signaling- A second difi'ereuce in the circuit arrangement of the link-circuit illustrated in Figure 3, over that illustrated in Figure 1, consists in means for locking the relay 90 of Figure 3 (corresponding to relay 90 of Figure 1) over the sleeve strand 71 and cut-ofl relay 1 of the busy line into which a plug has been inserted, instead of locking the relay 51 over the corresponding circuit including the said cut-off relay 1 as shown in the system of Figure 1. To this end, relay 90 is preferably provided with a connection to an inits initial energization, which is controlle by the movement of armature-switch 74 of the polarized-relay 70 to the right, is Secured through both sections 90 and 90 of said windings, and whereby the said relay 90, upon the attraction of its armature-spring 73 will lock itself through winding 90, alternate-contact of armature-switch 73, sleeve-strand 71 and cut-off relay 1 of the busy line.

It is to be understood that the condition of the apparatus, shown in Figure 3, is a transitory position, illustrates the connection of a calling subscriber A with a busy subscriber B, and that the polarized-relay 70, which has been momentarily attracted to close its armature-switch 74 with its right hand contact, has not as yet been retracted to its normal position, although the circuit through said magnet 70 has been already opened at the normal-contact of armatureswitch 7 3 Similarly, it is to be understood in the said Figure 3 that although the releasing-current is now being sent through the release-magnet 26' of vthe calling sub-' scribers' line to cause its energization'and operation, yet the attraction of its armaturesprings .has not as yet taken place. The energization of relay90, over the circuit already traced, caused the attraction of armature-spring 112 to close its contact and to place a direct groundconnection on the tip-conductor 47 of the link-circuit, thus short-circuiting tip-relay 52 and causing the release of its armature-springs; whereby the releasing current is sent from common bat- III.

i tery Cover conductor 6,-thr.ough lamp 38,- armature-switch 56 and its normal-contact, arm'ature-switch 54 and its normal-contact,

armature-switch 42 and its alternate-contact,-

conductor 25, switch a'rm -16, releasing magnet '26, and to the ground at switch 28 thus causing the release of the calling subscribers line in the manner already set forth I ductor: 48 from the calhngline at rotatingv at length in connection with the systemof re 1. The disconnection of sleeve-consPwitch-arm 17 willopen the circuit of sleeve- ,relay'51 in the system of Figure 3, thus spending relay 51 was maintalned in an encausing the release of its armature-springs; whereas, in the system of Figure 1, the cone er zed condition over the line and cutofi re any of the busy. called-forsubscribers line. In the system of Figure'3v the illu mination of the supervisory-lamp 35, now acting as a disconnect-mg signal, is securedby the'closing of a circuit through said lamp from battery-C, over conductor 120 and alternate-contact of armature-switch 110, to ground; The-operatorthus immediately se-' cures the. disconnecting signal by the illu mination of '{the supervisory-lamp associated with the calling subscriber-7s line (and by the sup lemental illumination ofthe pilot disconnecting lamp 33), entirelyjndepend- .ent-of'the condition of the supervlsory lamp 1 39, associated with .the called subscriber. The operator will therefore disconnect the erable to maintain the link-circuit now dis link-circuit in a response to Ithe indication given by lamp 35, Prior to sodoing, however, and as already pointed out, it'is pref- I connected from the calling subscriber but still connected with a jack,.in a .busy condition. To this end, as soon as'relay 51 has released its armature-switch 42 to makecontact with its normal-contact, a ground connection is placed upon conductor 25 of said link-circuit by the armature-switch "111 and its alternate-contact, controlled by reindicate that the line was busy because its' In other particulars, the arrangement of I i the link-circuitof Figure 3 is similar'to that shown in Figure 1"; and the operations of .the relays 76 84 and 78, when a plug is inserted into an idle line, are similar tothe operations of the corresponding relays 76,

I84 and 78 of Figure 1.

c In the said system of Figure 3, it has been assumedthat the line. into which the connecting plug 58 has been inserted, was a busy line. The heavy lines associated with said right hand subscribers 'line'in this case,

subscriber had initiated a call, (said subscriber having found the first link-circuit idle and having made. connection thereto,'as indicated by-the position of the switch-arms 3, 17 and 18 associated with said right hand subscriber) whereas, in the description Figure '1, it was assumed thata plu had reviously been connectedwith the sai busy.

ine. It will be apparent that, in eithercase, the busycondition ofthe line is determined by the existence of a connection to the active given of a-busy line inconnectionwith I terminal of the battery C (in one case through relay 76 and'in' the other through the two embodiments of the invention shown for connecting the answering-ends of link circuits with calling lines, there are features of my invention that need not be limited in their application to systemsof the class illustrated, One of the features, for example, whose use need not be limited .to-systems of the class illustrated is the provision of means whereby a clearing-out signal ma be conve ed to the operator when she ma es connection with'the multiple jack of a busy line, so that she may'immediately withdraw the plu without waiting for further signals. This is accomplished by the illumination of supervisory-lamp 35in both s stems. -As described in connection with ig. 1, both lamps 35-39 may light. As described in connection with Fig. 3, the clearing-outlamp 35 onlylights. Inex is always subject to operation by the calling 'subscribers switch-hook. It is now custo-' mary to provide another supervisory si al associated with the called subscribers ine, which will indicate prior to the called subscribers response and which will therefore also indicate when he replaces his telephone uponits hook. The latter signal is not a clearin -out signal.

change practice each clearing-out indicator Anot er feature of my invention that is not limited to either of .the exchange systems illustrated, resides in the automatic control of the association of the ringing-generator with a' called line. I

While the invention has been shown in connection with metallic circuit multiple switch-board systems, the invention need not be limited to metallic circuits nor'to'multiple switch-board systems, in all embodiments thereof.

I have shown two embodiments of the invention to illustrate the widev ap lication thereof, but as other applications 0 the in-. vention and various features thereof will be readily understood bythose skilledin the art I do not deem illustrations vof other to an understanding thereof.

embodiments of the invention to be essential The busy indication placed upon the calling subscrlbers line isobviously not limited to systems employing theappara tus for connecting lines in conversation, that is illustrate 'talking-strands of the link-circuits.

It will be also seen that the clearing-out feature of my invention need not be limited in its use to multiple switch-boards. For example, in the system shown it will be useful even though each line were provided with but one jack in addition to the automatic selecting-switch, for this feature of my invention would be operative if a plug were inserted into the jack of a called line that had been previously connected with the answering-end of some other link-circuit, whether or not the connecting-end of said other link-circuit were in service.

By a line already busy, as the expression is herein used, is meant a line with which the answering-end of a link-circuit is connected, or a line into a jack of which a connecting plug has been inserted.

It is obvious that changes may be made in the system of my invention as shown without departing from the spirit thereof,

and I do not, therefore, wish to be; limited to the same, but, having thus described my invention, I claim as new and desire to se cure by Letters-Patent:

1. A telephone exchange system including telephone lines extending to an exchange and provided with jacks, link-circuits at the exchange provided with manually operated terininals for connection with said jacks, clearing-out signaling-appliances in association with the link-circuits, a source of cur-- rent, and means associated with said source of current for causing the operation of the clearing-out signaling appliances upon the connection of said manually operated terminals with said jacks only when the jack connected to is that of an already busy line.

2. A telephone exchange system including telephone lines extending to an exchange and provided with jacks, link-circuits at the exchange provided with manually operated terminals for connection with sald jacks, clearing-out signaling-appliances .in association with the link-circuits, a source of current, and means associated with said source of current operating when the connecting-end of a link-circuit is connected with a line already busy for causing the operation of the clearing-out signaling-appliance associated with said link-circuit, said signaling-appliances each including a signal-o rating device associated with the, answerl l g-end of the cor respondin' link-circuit. 3. A to ephone exchange ing. telephone lines extending to an exchange and provided with jacks, link-circuits at the exchange provided with manually operated terminals for connection with said jacks, clearing-out signalin -appliances in association with the link-circuits, a source of current, and means associated with said sourceof current operating-when the connectingend ofa link-circuit is connected with a line already busy for causing the operation of the clearing-out signaling-appliances associated with said link-circuit, sald signaling-appliances each including a signal-operating device associated with the answerin -end of the corresponding link-circuit, sai signalappliances being controllable by the appasystem includratus of the calling telephone line when the associate link-circuit is connected with said calling telephone line and; prior to the connection of said link-circuit with the called telephone line alread 'busy.

4. A telephone ex ange system including telephone lines extending to an exchange and there provided with 'acks, link-circuits at the exchange provi ed with manual] operated terminals for connection with said jacks, clearing-out signaling-appliances whose circuits are determined by talkingstrands of the link-circuits, a source of our rent, and meansassociated with said source of current for causing the operation of the clearing-out signaling appliances upon the connection of said manually operated terminals with said jacks only when the 'ack connected to is that of an already busy iinef 5. A telephone exchange system including telephone lines extending to an exchange and there provided with jacks, link-circuits at the exchange provided with manually operated terminals for connection with said jacks, clearing-out signaling-appliances whose circuits are determined by talkingstrands of the link-circuits, a source of current, and means associated with said source of current operating when the connectingend of'a link-circuit is connected-with a line already busy for causing the operation of the clearing-out signaling-appliance associated with said link-circuit, said signaling-appliances each including a signal-operating-device associated with the answering-end of the corresponding link-circuit.

6. A telephone exchange system including telephone lines extending to an exchange and providedwith jacks, link-circuits at the exchange provided with manually. operated terminals for connection with said jacks, clearing-out signaling-appliances in association with the link-circuits, a source of ourcurrent operating when the connectingend TIE" ready busy for causing of a link-circuit is'connected with a line alr the operation of the clearing-out signaling-appliance associated;

with said link-circuits, automatically operated selecting-mechanism for connectlng the answe'rin -ends of the link-circuits; with calling ephonelines, automaticallyoperanswering-ends for efiecting the disconnectelephone lines and the the link-circuits; and

ated tion between-callm -mechanism associated with said link-circuit rent,

, ready rated after association with busy lines to ect" the actuation of the disconnecting mechanism. 7. A telephone exchange system including telephone lines extending to an exchangean provided with jacks, link-circuits at the exchange provided with manually operated terminals for connection with said jacks,

clearing-out signaling-appliances in association with the-link-circuits, a source of curmeans associated with said source of current operiatin -when'the connecting-end of a link-circuit is connected with a line albusy for causing the operation of the clearing-out signaling-appliance associated with said link-circuit, said signaling-appliances each including a signal-operating device associated with the answering-end of the correspondm link-circuit,automaticallyoperated selectmg-mechanism for connecting the answering-ends of the link-circuits with calling telephone lines, automatically operated mechanism for e'flecting the disconnection between calling telephone lines and the answering-ends of the hnk-circnits, and- '7 mechanism associated with said link-circuits to effect the actuation of the mechanism.

telephone of a link-circuit operated after association with busy lines disconnecting 8. A telephone exchange system including lines extending to an exchange. and provided with jacks, link-circuits at the exchange provided with manually operated terminals for connection with said jacks, clearing-out signaling-appliances in association with the link-circuits, a source of current, means associated with said source of current operating when the connecting-end is connected with a line already busy for causing the operation of the clearing-out signaling-appliance associated with said link-circuit; said signalingthe-.answering-ends calling telephone lines, automatically operapplianoes each including a signal-operating device associated with the answering-end of the corresponding link-circuit, said signalappliance's being controllable by the apparatus of the callingtelephone 'line when the associate link-circuit is connected with said calling telephone line and prior to the connection of. said link-circuit with the called telephone -linealready busy, automatically operated hating-mechanism for connecting of the link-circuits with clearing-out ated mechanism for efiecting the disconnec= tlon between calling telephone lines and the answering-ends of the link-circuits and mechanism associated with said link-circuits operated after association with busy lines to efiect the actuation of the disconnecting mechanism.

-9. A telephone exchange system including telephone lines extending to an exchange an the exchange provided with manually operated term nals for connection with said jacks, clearing-out- {signaling-appliances. whose circuits are determined by talking- -there provided with jacks, link-circuits at strands of the link-circuits, a source of current, means associated with said source ofcurrent' operating when the connecting-end of a link-circuit is connected with a'line al-v ready busy for causing the operation of the clearing-out signaling-appliance. associated with said link-circuit, automatically operated selecting-mechanism for connecting the answering-ends ofthe link-circuits with calling-telephone lines, automatically operated mechanism for effecting the disconnection between callin telephone lines and the answering-ends o :the link-circuits, andmechanism associated with said link-circuits ogerated after association with busy lines to e ect the actuation of the disconnecting mechanism. 1 s

10. A telephone exchange system including telephone lines extending to an exchange and there provided with jacks, link-circuits at the exchange provided with manually operated terminals for connection with said ]acks, clearing-out signaling-appliances whose circuits are determined by talkingxstrands ofthe link-circuits, a [source of curlOl operated after association with busy lines to efiect the actuation of the disconnecting mechanism. J I

11. Av telephone exchange system including telephone lines extending to an exchange and provided with jacks, link-circuits at the exchange provided with manually operated terminals for connection with'said jacks,

signaling-appliances in association with the link-circuits, a source of curl of a link circuit is'connected with a line a1- ready busy for causing the operation of the switching mechanism operating to effect the clearing-out signaling-appliance associated with said link-circuit, means for producing characteristic disturbance, and switching mechanism operatingto eifect the application of said characteristic disturbance upon a calling line that has been connected with the line already busy.

12. A telephone exchange'system including telephone lines extending to an exchange and provided with jacks, link-circuits at t e exchange provided with manually operated.

terminals for connection with said jacks, clearing-out signaling-appliances in association with the link-circults, a source of current. means associated with said source of current operating when the connecting-end of a link-circuit 1s connected with a line already busy for causing the operation'of the clearing-out signaling-appliance associated with said link-circuit, said signaling-appliances each including a signal-operating de- 'vice associated with the answering-end of the corresponding link-circuit, means for producing characteristic disturbance. and

application of said characteristic disturbance' upon a cal'ing line that has been connected with the line already busy.

13. A telephone exchange system including telephone lines extending to an exchange and provided with jacks, link-circuits at the exchange provided with manually operated terminals for connection with said jacks,

1 clearing-out signaling-appliancesin association with the link-circuits, a source of current, means associated with said source of current operating when the connection-end of a link-circuit is connected with a line already busy for causing the operation of the clearing-out signaling-appliance associated with saidlink-circuit, said signaling-appliances each including a signal-operating dc- "1C8. associated with the answering-end of the corresponding link-circuit, said signalappliances being controllable by the apparatus of the calling telephone line when the associate link-circuit is connected withsaid caling telephone line and prior to the connection of said link-circuit with the called telephone line already busy. means for producing characteristic disturbance. and switching mechanism operating to effect the application of said characteristic disturbance upon a calling line that has been connected with the line already'busy.

14. A teephone exchange system including telephone lines extending to an exchange and there provided with jacks,'link-circuits at theexchange provided with manually operated terminals for connection with said jacks, clearing-out signaling-appliances of a link-circuit is connected with a line alwhosecircuits are determined by talkingstrands of the link-circuits, a source oft current, means associatedwith said source of current operating when the connecting-end l0 ready busy for causing the operation ofthe' clearing-out signaling-appliance associated with said'link-circuit, means for producing "characteristic disturbance, and switching mechanism operating to effect the application. of said characteristic, disturbance upon a calling line that has been connected with the line already busy.

d5, Atelephone exchange system including telephone lines extending to an exchange and there provided with jacks, link-circuits at the exchange provided withmanually operated terminals for connection with said jacks, clearing-out signalin -appliances whose circuits are determined by talkingstrands of the link-circuits, a source of current, means associated with said source of current operating when the connecting-end of a link circuit is connected with a line already busy for causing the operation of the clearingsout signaling-appliance associated with said link-circuit, said signaling-appliances each including a signal-operating-device associated with the answering-end of the corresponding link-circuit, means for as producing characteristic disturbance, and switching mechanism operating to effect the application of said characteristic disturbance upon a calling line that has been connected with the line already busy.

16. A telephone exchange system including telephone lines extending to an exchange and provided with jacks. link-circuits at the ex-' change provided with annually operated terminals for connection with said acks, clearing-out signaling-appliances in association with the link-circuits, a source of current. means associated with said source of current. operating when the connecting-end of a linkcircuit is connected with a line already busy for causing the operation of the clearing-out s gnaling-appliance associated with said link-circuit, automatically operated selecting-mechanism for connecting the answering-ends ot' the link-circuits with calling ating to effect the application of said characteristic disturbance upon a calling line ghat has been connected with the line already usy.

f 17. A telephone exchange systemincludmg telephone lines-extending to an exchange and provided with jacks, link-circuits at the exchange, provided with manually operated terminals for connection with said jacks, clearing-out signaling-applfances in associa tion with the link-circuits, a source of current, means associated with said source of current operating when the connecting-end .of a link-circuit is connected with a line already busy for causing the operation of the clearing-out signaling-appliance associated with said link-circuit, said signaling-appliances each including a signal-operating device associated with the 'answering-end of the corresponding link-circuit, automatically operated selecting-mechanism for connecting the answering-ends of the link-circuits line that has been connected with a line already busy. i

18. A telephone exchange system including telephone lines extendin to. an exchan e and provided with jacks, lin -cir'cu its at t 19 exchange provided with manually operated terminals for' connection with said jacks, clearing-out signaling appliances in assocfation with the link-circuits, a source of current, means associated with said source end of a linkcircu' is connected with a line already busy for causing the operation of of current operatiyig when the connecting-- the clearing-out signaling-appliance asso-' ciated with said link-circuit, said signalingappliances each including a signal-operab ing device associated with the answering-end of thecorresponding link-circuit, said signaling-appli'ances being controllable by the and the answering-ends of apparatus of the calling telephone line when the associate link-circuit is connected with said calling telephone line 'and 'prior to the connection of. said link-circuit with the called telephone line already busy, automatically operated selecting-mechanism for connecting the answering-ends of the link-circuits with calling telephone lines, automatically. operated mechanism for effecting the disconnect on between callin telephone lines the linkcircuits, mechanism associated with said link-circuits operated after association with busy. lines to effect the actuation of the disconnecting 'mechanism, means for producing character-- istic disturbance, and switching mechanism operating to efiect-the application of said characteristic disturbance upon a calling ciated with said link-circuits 0 line that has been connected with a line a lready busy. 1

19. A telephone exchange system includ-' ing telephone lines extending to an exchange and there provided with jacks, link-circuits 1 at the exchange provided with manually operated terminals for connection with said jacks, clearing-out signaling-appliances whose circuits are, determined by talking strands of the link-circuits, a source of current, means associated with saidsource of current operating when the connecting-end of a link-circuit is connected with a line already busy for causing the operation of the clearing-out signaling-appliance associated with said link-circuit, automatically operated selecting-mechanism for connecting the answeringends of the link-circuits with calling telephone lines," automatically operated mechanfsm for effecting the disconnection between calling tele hone lines and the answering-ends of the link-circuits, mechanism associated with said link-circuits operated after association with busy lines to' effect the actuation of the disconnecting mechanism, means for producing characteristic disturbance, and switching mechanism operating to effect the application of said characteristic disturbance upon a calling line that has been connected with the line already busy.

20. A telephone exchange system includ-- ing telephone lines extendin to an exchange and there provided wi circuits at the'exchange provided with manually 0 rated terminals for connection with said vjacks, clearing-out signaling jacks, linkappliances whose circuits are determined by talking-strands of the link-circuits, a source of current, means associated with said source 'of current operating when-the connecting end of va. link-circuit is connected with a line already busy for causing the operation of the clearing-out signalingappliance associated with said link-circuit, said signaling-appliances each including a signal-operating device associated with the answering-end of the corresponding linkcircuit, automatically operated selectingmechanism for connecting the answeringends of the link-circuits with calling telephone lines, automatically operated mechanism for effecting the disconnection between calling telephone lines and the answeringends of the link-circuits, mechanism assorated after association with busy lines to e ect the actuation of the disconnecting mechanism,'means 'for producing characteristic disturbance, and

switching mechanism operating to effect the application of said characteristicdisturb ance upon a calling line that has :beenconnected with the line already busy.

21. Avteleph'one exchange system'ific'ludsource of current, and means associated ing telephone lines extending. to an exchange and provided with Jacks, link-circuits provided with manuallyoperated ter. minals for making connection with the jacks, automatically operating selecting mocha nis'm for connecting the answering-ends of link-circuits with calling lines, automatically operating releasing mechanism for efiecting disconnection between the answer-- ing-ends of link-circuits and calling lines, a

with said source of current operating after the connecting end of a link-circuit is con nected with a line already busy-for causing the operation of the said releasing-mechanism associated with said link-circuit.

, 22. A telephone exchange system including telephone lines extending to an exchange and provided with jacks, link-clr cuits provided with manually operated terminals for makin connection with the jacks, automatically operating selecting mechanism for connecting the arlsweringends f'link-circuits with calling lines, automatically operating releasing mechanismfor effecting disconnection between the answering-ends of link-circuits and calling lines, a

source of current, means associated with said source of current operatmg after the con necting end of a link-circuit is connected with a line alreadybusy for causing the operation of the said releasing-mechanism associated with said link-circuit, means for producing characteristic disturbance, and switching mechanism operating to effect the 7 application of said characterlstic disturbance upon a calling line that has been connected with a line already busy.

23. A telephone exchange system including telephone lines extending to an exohange and provided with jacks, link-cir cuits provided with manually operated terminals for making connection with the jacks, automatically operating selecting mechanism for connecting the answeringends of link-circuits with calling lines, automatically operating releasing mechanism for effecting disconnection between the answering-ends of link-circuits and calling lines, means for producing characteristic disturbance, and means associated with the link-circuits operating after thelink-circuits have been connected with called lines already busy, for effecting the application of said means for producing characteristic disturbance upon calling telephone lines.

' 24. A telephone exchange system including telephone lines extending to an exchange and provided with two-contact jacks, linkcircuits at the exchange provided with twocontact manually operated terminals for connecting with said jacks, automatic means for connecting calling ones of said lines with idle ones of said link circuits, a source .of signaling current, a switching appliance the substation therwf, andmeans for autoassoeiatedwith-said source; of current" eratlng, when the connecting end of a linkc rcuit is connected with an idle called; line, "to connect said source with said line to'signal maticallyu extending a busy si' al toa callr. ing line" that hasbeen comfia ted with .a called line already busy.. p

25. Ajtelephone system includin a.telephonelme, terminal contacts there or at. the exchange including talking contacts for exvtending the conversational circuits of said line, a connection'terminal having a contact adapted to-en'gage; one of said talking contacts, and electromagnetic means initially controlled over a circuit includi said one jof sa d talking contacts and said'contactoi said connection terminal to automatically connect a source of signaling current wit saldfconnection terminal.

1 26. A' telephone s stem including a call ingline anda calle line, terminal contacts for said called line at the exchange including talking contacts for extending the conversational circuit oi? said line, alink-circuit temporarily connected with the calling line, a connection terminal therefor havin a contactifor engagement with one of sald talkmg contacts, mechanism adapted for connection with the calling lineto transmit a busy signal thereover, means forautomatically connecting calling current to the called line and a circuit automatically controlling the transmission of said signal before the operation of said means if said called line is busy including said one of said talking contacts and said contact of said connection terminal.

27. A telephone system including a calling line and a called line, terminal contacts for each of said lines at the exchange including talking contacts, a link-circuit at the ex- .change for connecting talking contacts of each of said lines to form a conversational circuit between said lines, a source of calling current adapted for connection with the called line, mechanism adapted 'for connection w th the calling line to transmit a busy signal thereover, and apparatus sensitive to the idle or busy condition of the called line controlled over a circuit including a por- 115 tion of said link-circuit and said one of said talking contacts for automatically completingconnection of said source or of said mechanism accordin to the idle or busy condition of the calle line. 12

28. A telephone system including telephone lines, terminals for said lines at the exchange, a link-circuit for establishing connections between the terminals of calling and called lines,'mechanis'1n ,adapted to be 125 operated to connect calling current to the called line if idle, and means for automatically transmitting a busy signal to a calling subscriber controlled over a circuit including a talking contact of a terminal of the phone lines, terminals for said lines at the exchange, a link-circuit for establishing connections with called lines, automatic means for connecting calling lines with said link circuit, a source of signalling current adapted for connection with a called line, and mechanism for automaticall connecting said source in circuit with t e called line controlled over a circuit including a talking contact of a terminal of said line.

30. A telephone exchange system com rising a plurality of subscribers telep one lines, a pluralityl of associated link-circuits, automatic switc in connection between a calling line and an id e link-circuit, operators means for extending the circuit of a selected link-circuit to a-called line, supervisory signals associated with the calling and answering ends of said link-circuits, and means operative upon the extension of said circuit to a busy called line to display both of said supervisory signals.

31. A telephone exchange system com rising a plurality of subscribers telep one lines, a pluralit of associated link-circuits, automatic switch mechanism for establishin connection between a calling line and an idle link-circuit, o erators plug and jack connecting means or connecting aselected link-circuit to a called line, supervisor signals associated with the calling an answering ends of said link-circuits, and means operative upon the establishment of the plug and jack connection with a busy called line to display both of said supervisory signals.

32. A telephone exchange system comprising a telephone line, a plurality of associated link-circuits, automatic switch mechanism res onsive to certain electrical conditions on sai line to establish connection between said line and an idle link-circuit, and means under the control of an operator for displaya ing a signal to indicate the existence of ing a telephone line, a

the said actuating electrical conditions on the line.

33. A telephone exchange system comprising a telephone line, a plurality of associated link-circuits, automatic switch mechanism responsive to certain electrical conditions on said line to establish connection between mechanism for establishresponsive to certain electrical conditions on said line to establish connection between said line and an idle link-circuit, operators means for answering a call, and means under the control of the operator for displaying a signal in the event of a false call.

35. A telephone exchange system comprising a plurality of telephone lines, a plurality of associated link-circuits, a plurality of switch mechanisms individually operative in response to certain electrical conditions on a calling line to establish connection between that line and an idle link-circuit, and means under the control of an operator to indicate the existence of the actuating conditions on said calling line and to free the connected link-circuit so that it may "be selected. by other switch mechanisms.

36. A telephone exchange system comprising a plurality of subscribers telephone lines, a plurality of associated link-circuits, a plurality of switch mechanisms individually operative in response to certain electrical conditions on a callin line to establish connection between that line and an idle link-circuit, operators means for extending the circuit of a selected link-circuit to a called line, and means under the control of the operator to indicate the existence of the continued actuating conditions on said calling line and to free the connected link-circuit so that it may be selected by other switch mechanism.

37. A telephone exchange system com. ris- V ing a plurality "of subscribers telep one lines, a plurality of associated link-circuits,

a plurality of switch mechanisms individually responsive to certain electrical conditions on a calling line to establish connection between that line and an idle link-circuit, operators means for answering a call, I

' switch mechanisms.

38. In combination with an' operators link-circuit, a source of ringing current, a relay magnet individual to said link-circuit for periodically applying said source to a terminal of said circuit, means for causing such periodical operation of said rela a second relay also controlling the circuit rom said source to said terminal, and a third response supervisory relay for exercising control over said first-mentioned rela 39. A telephone system inclu ing .'telephone lines, a link-circuit for interconnecting calling and called lines, a source of signalling current, a relay magnet individual to said circuit adapte for periodic operations and controlling the application of said source to called lines, means for causing such periodical operations of said relay, and a second response supervisory relay magnet 

